Light emitting element and producing method thereof, and display device and lighting device using the same

ABSTRACT

An organic light-emitting device  10  has the constitution in which an emission region  3  between an anode  2  and a cathode  4  is laminated on a substrate  1 . The emission region  3  includes polymer  3 A, luminous molecules  3 G which are material contributable to emission, and charge transport material  3 F. 
     The luminous molecules  3 G and the charge transport material  3 F are high in concentration at a side close to the cathode  4  and low in concentration at a side close to the anode  2  in a layer thickness direction of the emission region  3 . The organic light-emitting device can be formed by luminous material, or luminous material and charge transport material being penetrated into polymer, or polymer in which charge transport material is dispersed, thus providing highly improved luminous efficiency and at the same time facilitating the patterning.

TECHNICAL FIELD

The present invention relates to a light-emitting device used as a flatlight source and a flat display.

BACKGROUND ART

Electric field light-emitting devices, which have self-luminous propertyand thus high visibility and excellent display capability and enablehigh speed response and low-profile, are now attracting the attention asdisplays for flat displays and the like.

Among others, an organic EL device, using organic compound as phosphor,has characteristic features, as compared with inorganic EL device, thatit can be driven at a low voltage, that it can easily produce anenlarged area, and that it can easily produce a desired luminous colorby an appropriate choice of coloring matter and, accordingly, theorganic EL device is now vigorously developing as a next-generationdisplay.

The EL device using the organic phosphor generates blue luminescence forexample, through the application of a voltage of 30 volts to ananthracene evaporated film having thickness of 1 m or less (Thin SolidFilms, 94(1982) 171). However, this device fails to produce sufficientluminance even when a high voltage is applied thereto, so that it isrequired to be further improved to have higher luminous efficiency.

In regard to this, Tang et al. teaches that transparent electrodes(anode), a hole transport layer, an emission region having electrontransport capabilities, cathode using metal of low work function arelaminated for reduction in voltage and improvement in luminousefficiency, to thereby produce luminance of 1,000 cd/m² through theapplication of a voltage of 10V or less (Appl. Phys. Lett. 51 (1987)913). Used as the phosphor is tris (8-quinolinolato) aluminum complex(hereinafter it is referred to as “Alq”). The Alq is an excellentluminophor having both high luminous efficiency and high electrontransport capability.

Further, a device having a three-ply structure wherein an emissionregion is sandwiched between a hole transport layer and an electrontransport layer and a device that obtains luminescence from coloringmatter (coumarin derivative or fluorescent dye, such as DCM1, used tothe Alq) doped in the emission region is reported (Jpn. J. Appl. Phys.,27 (1988) L269 and J. Appl. Phys., 65(1989) 3610). The report says thatit is discovered that an adequate choice of the coloring matter canallow luminous color to change and can produce improved luminousefficiency, as compared with the non-doped one.

In the devices constructed above, all layers are formed by dry processsuch as a vacuum evaporation method. On the other hand, the method hasbeen proposed of producing the device in the so-called wet depositionprocess such as a spin coat method and a cast method (Japanese Laid-open(unexamined) Patent Publications No. Hei 3-790 and No. Hei 3-171590).

In this method, at least one material for forming the hole transportlayer, the electron transport layer and the emission region is dissolvedin appropriate solvent, together with polymer binder. Then, thatsolution is applied onto the electrode to form the emission region and,thereafter, a further electrode is formed on the emission region in theevaporation method or a like method. Hereinafter, the organiclight-emitting device thus produced is called “polymer dispersedlight-emitting device”, in contrast to the conventional laminatedlight-emitting device.

When comparing with the organic light-emitting device produced by thedry process, the polymer dispersed light-emitting device has thefollowing advantages.

(1) Even the material for which it is hard to be deposited in the dryprocess such as evaporation can be used;

(2) Even the doping of minute amounts for which it is hard to becontrolled in the dry process can be performed with ease;

(3) An enlarged area can be produced with ease;

(4) The device can be produced at low costs;

(5) Simultaneous luminescence from luminous molecules is enabled withease through the introduction of a number of luminous molecules (whiteluminescence is enabled); and

(6) In the conventional laminated light-emitting device, the layers areeach in the amorphous state. In contrast to this, in the polymerdispersed light-emitting device, the materials are dispersed in thepolymer binder. Accordingly, the latter is thermally stable as comparedwith the former.

The conventional polymer dispersed light-emitting devices comprise theemission region in which perinone derivative or tris (8-quinolinolato)aluminum used as the luminous molecules is dispersed ill polyvinylcarbazol or the emission region in which tris (8-quinolinolato) aluminumand tetraphenyl benzidine used as the luminous molecules are dispersedin polycarbonate (Japanese Laid-open (unexamined) Patent PublicationsNo. Hei 3-790, No. Hei 3-171590).

(First Problem)

The polymer dispersed light-emitting device has the advantages mentionedabove, while on the other hand, it has the disadvantage that it is lowin luminous efficiency, as compared with the conventional laminatedlight-emitting device.

Specifically, in the laminated light-emitting device, holes are injectedfrom the anode to the hole transport layer, and electrons are injectedfrom the cathode to the emission region of the electron transportcapability or the electron transport layer. When these holes andelectrons are recombined in the emission region, excitons are formed,and when the excitons are caused to transition to the ground state, theemission takes place. It is to be noted that the electron transport andthe hole transport are functionally separated from each other, so thatthe recombination of the electron and hole takes place only in thevicinity of an interface between the adjoining layers. This can producethe efficient production of the excitons and thus improved luminousefficiency.

Further, through an appropriate choice of the material of the layersadjoining the respective electrodes to minimize injection barriersbetween the anode and the cathode, the injection of the hole and theelectron can be facilitated, and as such can allow the drive at a lowvoltage.

In contrast to this, the polymer dispersed light-emitting device mainlycomprises a monolayer, so that the recombination of the hole andelectron and the production of the excitons do not take place locally,differently from the laminated light-emitting device mentioned above. Inaddition, the barriers for the hole and the electron to be injected fromthe electrodes are high. These facts make it difficult to improveluminous efficiency.

Thus, the emission site is dispersed over the whole emission region, sothat it is hard to balance the injection of the hole and electron andthe transport of the same. As a result of this, the probability of therecombination reduces, such that sufficient luminous efficiency is notproduced. This indicates that collection of the recombination region ofthe hole and electron into a specific region leads up to improvement inluminous efficiency.

Though the method of laminating the functionally separated layers is ofeffective, as mentioned above, in a polymeric system formed by coating,solvent contained in polymer solution of a second layer to be laminatedover a first deposited layer must be chosen to prevent the firstdeposited layer from being dissolved in that solvent.

In addition, as the laminated-layers increase in number, the need tochoose the solvent and the need to choose the material soluble in thatselected solvent arise increasingly. This arises the problem that therange of choice for the material is further narrowed, thus hindering theeffectively improved efficiency.

(Second Problem)

Further, the polymer dispersed light-emitting device involves theproblem that when a color panel is produced, it is difficult to do thepatterning (distribution of application of color). When the color panelis produced in the dry process such as the vacuum evaporation method,elements of color can be formed in desired positions by an evaporationmask being set on a substrate. In contrast to this, in the wetdeposition such as the spin coat method or the cast method, since theemission region is formed over the whole area of the substrate, theabove-mentioned patterning cannot be performed.

In regard to this, the patterning using an ink-jet method has beenproposed (e.g. Japanese Laid-open (unexamined) Patent Publication No.Hei 10-12377). This proposes that material of the emission regionincluding polymer or the precursor of polymer is discharged from nozzlesby the ink-jet method to form a desired pattern.

However, the patterning using the conventional ink-jet method involvesthe problem that polymer solution or equivalent to be coated is high inviscosity, so that the nozzles of the ink head are easily plugged upand, accordingly, it is difficult to form a micropattern.

To solve the problems mentioned above, the present invention has beenmade. The present invention provides an organic light-emitting devicecapable of producing highly improved luminous efficiency and at the sametime facilitating the patterning even in the polymer dispersed organiclight-emitting device and the producing method thereof.

DISCLOSURE OF THE INVENTION

In the light of the current situation, a group of inventions have beenmade. The object of the invention is to provide a light-emitting devicehaving high luminous efficiency.

Although the group of inventions is based on the same or similarconception, since they are realized by way of different embodiments, theinventive groups are divided into the first inventive group and thesecond inventive group on the basis of their respective relevance in thespecification. In the following, the contents will be explained in orderfor each division (each inventive group).

First Inventive Group

After having devoted themselves to the studies in order to attain theobject, the inventors of this application have found that in producing apolymer dispersed light-emitting device, a polymer layer is first formedand then luminous molecules, or luminous molecules and charge transportare penetrated in the polymer layer thus formed, thereby producing ahighly improved luminous efficiency and at the same time facilitatingthe patterning.

Specifically, a first aspect of the invention is directed to alight-emitting device having an emission region between an anode and acathode, wherein the emission region comprises material contributable toemission and a medium for containing the material, and wherein thematerial contributable to the emission has a substantially successivedistribution of concentration from the anode side of the emission regiontoward the cathode side thereof.

A second aspect of the invention is directed to the light-emittingdevice as set forth in the first aspect of the invention, wherein thematerial contributable to the emission exhibits the distribution ofconcentration according to which any one of the anode side of theemission region and the cathode side thereof is higher in concentrationthan the other, and the concentration reduces from the one side towardthe other side successively.

With this constitution, in a region where the material contributable tothe emission in the emission region is high in concentration, the holeinjected from the anode into the emission region and the electroninjected from the cathode into the emission region are recombined. Thus,the recombination region of the hole and the electron is collected, sothat the recombination efficiency of the electron and the hole isincreased and thus the luminous efficiency is improved.

The terminology “material contributable to emission” is intended toinclude, for example, material that form organic binder, chargetransport material and dimmer, excimer, or exciplex to obtain emissiontherefrom, in addition to the luminous molecules that emit light by theinjection of electric charge as shown in Embodiments as will bementioned later. It is noted here that the terminology of the dimmermeans material combined with the organic binder or the charge transportmaterial in the ground state and the terminology of the excimer and theexciplex means material caused to react with the organic binder or thecharge transport material in the excitation state caused by theinjection of the charge.

A third aspect of the invention is directed to the light-emitting deviceas set forth in the first aspect of the invention, wherein the emissionregion further comprises charge transport material.

The charge transport capabilities in the emission region are furtherimproved and thus the recombination efficiency of the electron and thehole is improved.

A fourth aspect of the invention is directed to the light-emittingdevice as set forth in the third aspect of the invention, wherein thecharge transport material has a substantially successive distribution ofconcentration from the anode side of the emission region toward thecathode side thereof.

With this constitution, a region large in hole transport capability anda region large in electron transport capability are formed in theemission region, as viewed in a direction extending from the anode sideto the cathode side (layer thickness direction), so that therecombination efficiency of the electron and the hole is improved.

A fifth aspect of the invention is directed to a light-emitting devicehaving a charge transport region between an anode and a cathode, whereinthe charge transport region comprises charge transport material and amedium for containing the charge transport material, and wherein thecharge transport material has a substantially successive distribution ofconcentration from the cathode side of the charge transport regiontoward the anode side thereof.

With this constitution, a region large in hole transport capability anda region large in electron transport capability are formed in theemission region, so that the recombination efficiency of the electronand the hole is improved. In the constitution above, the chargetransport region has luminescent properties and thus doubles as theemission region.

A sixth aspect of the invention is directed to the light-emitting deviceas set forth in the first aspect of the invention, wherein the emissionregion includes a region where the material contributable to theemission is not present.

With this constitution, a region different in carrier transportcapability is formed in the emission region, so that the recombinationefficiency of the electron and the hole is further improved and thus theluminance efficiency is improved.

A seventh aspect of the invention is directed to the light-emittingdevice as set forth in the first aspect of the invention, wherein a partof the emission region that exhibits the maximum concentration of thematerial contributable to the emission is away from the anode and thecathode.

The reason that the part of the emission region that exhibits themaximum concentration of the material contributable to the emission isaway from the both electrodes is that when the material contributable tothe emission is close to the anode or the cathode, there is thepossibility that the material contributable to the emission may beextinguished without emitting. The part of the emission region thatexhibits the maximum concentration of the material contributable to theemission is preferable at a substantially immediate position between theanode and the cathode.

An eighth aspect of the invention is directed to the light-emittingdevice as set forth in the fifth aspect of the invention, wherein thecharge transport region includes a region where the charge transportmaterial is not present.

With this constitution, in the boundary between the region where thecharge transport material is present and the region where the chargetransport material is not present a region, the recombination efficiencyof the electron injected from the cathode and the hole injected from theanode is further improved and thus the luminance efficiency is improved.

A ninth aspect of the invention is directed to the light-emitting deviceas set forth in the fifth aspect of the invention, wherein a part of thecharge transport region that exhibits the maximum concentration of thecharge transport material is away from the anode and the cathode.

A tenth aspect of the invention is directed to the lighting device usingthe light-emitting device as set forth in the first aspect of theinvention.

With this constitution, the lighting device having improved luminanceefficiency can be provided.

An 11th aspect of the invention is directed to a light-emitting devicehaving an emission region between an anode and a cathode, wherein theemission region comprises material contributable to emission and amedium for containing the material, and wherein the materialcontributable to the emission has a distribution of concentration thatreduces substantially successively in a direction parallel to a surfaceof the cathode and a surface of the anode from a substantially center ofthe emission region toward a periphery thereof.

A 12th aspect of the invention is directed to the light-emitting deviceas set forth in the 11th aspect of the invention, wherein there areprovided a number of materials contributable to the emissions and areadjacently arranged in a direction parallel to a surface of the cathodeand a surface of the anode, and wherein the materials contributable tothe emissions are different from each other in luminous color.

With this constitution, since the concentration is low in regions in thevicinity of the boundaries between the materials contributable to theemission, the materials contributable to the emission are prevented frombeing mixed with each other. Thus, the light-emitting device thatprovides excellent full color display capability with little colormixture is produced.

A 13th aspect of the invention is directed to the light-emitting deviceas set forth in the 11th aspect of the invention, wherein the emissionregion further comprises charge transport material.

A 14th aspect of the invention is directed to the light-emitting deviceas set forth in the 13th aspect of the invention, wherein the chargetransport material has a distribution of concentration that reduces inthe direction parallel to the surface of the cathode and the surface ofthe anode from the substantially center of the emission region towardthe periphery thereof.

A 15th aspect of the invention is directed to the light-emitting deviceas set forth in the 11th aspect of the invention, wherein the materialcontributable to the emission has a substantially successivedistribution of concentration from the cathode side of the emissionregion toward the anode side thereof.

With this constitution, since the material contributable to the emissionis made to have the distribution of concentration so that therecombination region of the hole and the electron is collected, therecombination efficiency of the electron and the hole is improved andthus the luminance efficiency is improved.

A 16th aspect of the invention is directed to the light-emitting deviceas set forth in the 14th aspect of the invention, wherein the chargetransport material has a substantially successive distribution ofconcentration from the cathode side of the emission region toward theanode side thereof.

With this constitution, the recombination efficiency of the electron andthe hole is further improved and thus the luminance efficiency isimproved.

A 17th aspect of the invention is directed to the light-emitting deviceas set forth in the 11th aspect of the invention, wherein the emissionregion includes a region where the material contributable to theemission is not present.

An 18th aspect of the invention is directed to the light-emitting deviceas set forth in the 11th aspect of the invention, wherein the medium forcontaining the material contributable to the emission has chargetransport capability.

A 19th aspect of the invention is directed to the light-emitting deviceas set forth in the 11th aspect of the invention, wherein the medium forcontaining the material contributable to the emission comprises organicmaterial.

A 20th aspect of the invention is directed to the light-emitting deviceas set forth in the 11th aspect of the invention, wherein the mediumcomprises polymer.

With this constitution in which the emission region comprises organicmaterial, or to be more specific, polymer, the organic light-emittingdevice having an improved efficiency is produced.

A 21st aspect of the invention is directed to a display using thelight-emitting device as set forth in the 11th aspect of the invention.

With this constitution, the display having an improved luminousefficiency is provided.

A 22nd aspect of the invention is directed to a producing method of alight-emitting device having an emission region between an anode and acathode, the producing method comprising: a disposing step of disposinga medium on the anode or the cathode; and a containing step of allowingmaterial contributable to emission to be contained in the medium to formthe emission region.

Since this method comprises the step of disposing the medium on theanode or the cathode and the step of allowing material contributable toemission to be contained in the medium, it can provide an effectivemethod when it is difficult to dispose the medium previously containingthe material contributable to the emission on the anode or the cathode.

A 23rd aspect of the invention is directed to a producing method of alight-emitting device having an emission region between an anode and acathode, the producing method comprising a disposing step of disposing amedium containing charge transport material on the anode or the cathode;and a containing step of allowing material contributable to emission tobe contained in the medium to form the emission region.

This method enables the charge transport material to be contained in themedium, and as such can produce the light-emitting device that caninject and transport the charge with efficiency.

A 24th aspect of the invention is directed to a producing method of alight-emitting device having an emission region between an anode and acathode, the producing method comprising a disposing step of disposing amedium on the anode or the cathode; and a containing step of allowingmaterial contributable to emission and charge transport material to becontained in the medium.

A 25th aspect of the invention is directed to a producing method of alight-emitting device having an emission region between an anode and acathode, the producing method comprising a disposing step of disposing amedium containing charge transport material on the anode or the cathode;and a containing step of allowing material contributable to emission andcharge transport material to be contained in the medium.

The charge of the charge transport material contained in the medium inthe disposing step and the charge of the charge transport material inthe containing step may be different from or identical to each other.

A 26th aspect of the invention is directed to a producing method of alight-emitting device having a charge transport region between an anodeand a cathode, the producing method comprising a disposing step ofdisposing a medium on the anode or the cathode; and a containing step ofallowing charge transport material to be contained in the medium.

A 27th aspect of the invention is directed to the producing method of alight-emitting device as set forth in the 23rd aspect of the invention,wherein in the containing step, the material contributable to theemission is penetrated into the medium, whereby it is contained in themedium.

A 28th aspect of the invention is directed to the producing method of alight-emitting device as set forth in the 24th aspect of the invention,wherein in the containing step, the material contributable to theemission and the charge transport material are penetrated into themedium, whereby they are contained in the medium.

This method provides the light-emitting device that enables the materialcontributable to the emission, or the material contributable to theemission and the charge transport material to have a substantiallysuccessive distribution of concentration from the anode side of thecharge transport region toward the cathode side thereof and vice versa.

A 29th aspect of the invention is directed to the producing method of alight-emitting device as set forth in the 23rd aspect of the invention,wherein in the containing step, solution obtained by the materialcontributable to the emission being dissolved in solvent is brought intocontact with the medium, whereby the material is penetrated into themedium.

A 30th aspect of the invention is directed to the producing method of alight-emitting device as set forth in the 24th aspect of the invention,wherein in the containing step, solution obtained by the materialcontributable to the emission and the charge transport material beingdissolved in solvent is brought into contact with the medium, wherebythe materials are penetrated into the medium.

This method also provides the light-emitting device that enables thematerial contributable to the emission, or the material contributable tothe emission and the charge transport material to have a substantiallysuccessive distribution of concentration from the anode side of thecharge transport region toward the cathode side thereof and vice versa.

A 31st aspect of the invention is directed to the producing method of alight-emitting device as set forth in the 27th aspect of the invention,wherein in the containing step, the material contributable to theemission is penetrated into the medium in an ink jet method.

The method above allows the material contributable to he emission topenetrate into the medium in the ink-jet method, so that when polymerhigh in viscosity is used as the precursor of the medium, the need ofthe application of the polymer solution and the material contributableto the emission in the ink-jet method can be eliminated. Therefore, thenozzles of the ink jet are prevented from being plugged and also finepatterns can be formed with ease.

Second Inventive Group

On the basis of the concept that collection of the luminous molecules,which were dispersed over the whole organic layer, to a specific regionand enlargement of the surface area of the organic layer lead toimprovement in efficiency of the polymer-based organic light-emittingdevice, the inventors of this application disperse the luminousmolecules on a front surface of the organic layer or in a region in thevicinity of the front surface of the same and thereby solve the problemsmentioned above.

Specifically, a 32nd aspect of the invention is directed to alight-emitting device having an emission region between an anode and acathode, wherein the emission region comprises material contributable toemission, and wherein a collecting means for collecting the materialcontributable to the emission to a specific region is provided betweenthe anode and the cathode.

To be more specific, a 33rd aspect of the invention is directed to alight-emitting device having an emission region between an anode and acathode, wherein at least one of an anode side of the emission regionand a cathode side thereof is made porous, and wherein materialcontributable to emission is included in a surface of the emissionregion which is made porous.

A 34th aspect of the invention is directed to a light-emitting devicehaving an emission region between an anode and a cathode, wherein atleast one of an anode side of the emission region and a cathode sidethereof is made porous, and wherein material contributable to emissionis included in a region in the vicinity of a surface of the emissionregion which is made porous.

With the constitutions above, the material contributable to emission iscollected to a specific region, or specifically, to a surface of theemission region which is made porous or to a region in the vicinity ofthe surface thereof and also the recombination region of the hole andthe electron in which the material contributable to emission is presentis enlarged. Thus, the emission with improved luminance can be produced.

A 35th aspect of the invention is directed to the light-emitting deviceas set forth in the 33rd aspect of the invention, wherein chargetransport material is included in a surface of the emission region whichis made porous.

A 36th aspect of the invention is directed to the light-emitting deviceas set forth in the 33rd aspect of the invention, wherein a leveledlayer comprising charge transport material is provided on a surface ofthe emission region which is made porous.

With this constitution, leakage of current is prevented and also theinjection and transport of the hole or the electron can be performedwith improved efficiency. Further, the leveled layer can permit thejoint surface of the adjacent anode and cathode to be kept smooth

A 37th aspect of the invention is directed to a light-emitting devicehaving a charge transport region between an anode and a cathode, whereinat least one of an anode side of the charge transport region and acathode side thereof is made porous.

With this constitution, the charge can be injected from the electrodes(anode and cathode) into the charge transport region with improvedefficiency. In this constitution, the charge transport region is aregion having the luminescent property and thus doubles as the propertyof the emission region.

A 38th aspect of the invention is directed to the light-emitting deviceas set forth in the 37th aspect of the invention, wherein the chargetransport region is a hole transport region.

A 39th aspect of the invention is directed to the light-emitting deviceas set forth in the 37th aspect of the invention, wherein the chargetransport region is an electron transport region.

A 40th aspect of the invention is directed to the light-emitting deviceas set forth in the 33rd aspect of the invention, wherein the emissionregion comprises an organic matter.

A 41st aspect of the invention is directed to the light-emitting deviceas set forth in the 33rd aspect of the invention, wherein the emissionregion comprises polymer.

A 42nd aspect of the invention is directed to a light-emitting devicehaving an emission region between an anode and a cathode, wherein atleast one of an anode side of the emission region and a cathode sidethereof is roughened, and wherein material contributable to emission isincluded in a surface of the roughened emission region.

A 43rd aspect of the invention is directed to a light-emitting devicehaving an emission region between an anode and a cathode, wherein atleast one of an anode side of the emission region and a cathode sidethereof is roughened, and wherein material contributable to emission isincluded in a region in the vicinity of a roughened surface of theemission region.

With these constitutions, the surface area of the recombination regionof the hole and the electron where the material contributable toemission is present is enlarged, thus producing the emission withimproved luminance.

A 44th aspect of the invention is directed to the light-emitting deviceas set forth in the 42nd aspect of the invention, wherein a leveledlayer comprising charge transport material is provided on a roughenedsurface of the emission region.

A 45th aspect of the invention is directed to a light-emitting devicehaving a charge transport region between an anode and a cathode, whereinat least one of an anode side of the charge transport region and acathode side thereof is roughened.

With this constitution, the charge can be injected from the electrodes(anode and cathode) into the charge transport region with improvedefficiency. When he emission region is located over the roughened chargetransport region, the contact area of the emission region and the chargetransport region is enhanced, so that the hole can be injected from theanode into the emission region with improved efficiency.

A 46th aspect of the invention is directed to the light-emitting deviceas set forth in the 45th aspect of the invention, wherein the chargetransport region is a hole transport region.

A 47th aspect of the invention is directed to the light-emitting deviceas set forth in the 45th aspect of the invention, wherein the chargetransport region is an electron transport region.

A 48th aspect of the invention is directed to the light-emitting deviceas set forth in the 42nd aspect of the invention, wherein the emissionregion comprises an organic matter.

A 49th aspect of the invention is directed to the light-emitting deviceas set forth in the 42nd aspect of the invention, wherein the emissionregion comprises polymer.

A 50th aspect of the invention is directed to a display using thelight-emitting device as set forth in the 33rd aspect of the invention.

A 51st aspect of the invention is directed to a lighting device usingthe light-emitting device as set forth in the 33rd aspect of theinvention.

With the constitutions above, the display and the lighting device havingimproved luminous efficiency can be provided.

A 52nd aspect of the invention is directed to a producing method of alight-emitting device having an emission region between an anode and acathode, the producing method comprising a medium disposing step ofdisposing a medium on the anode or the cathode; and a porosity producingstep of making at least a part of the medium porous.

A 53rd aspect of the invention is directed to a producing method of alight-emitting device having an emission region between an anode and acathode, the producing method comprising a medium disposing step ofdisposing a medium on the anode or the cathode; a porosity producingstep of making at least one of an anode side of the medium and a cathodeside thereof porous; and a disposing step of disposing materialcontributable to emission on a porous surface of the medium, so that theemission region is formed by the medium and the material contributableto the emission.

A 54th aspect of the invention is directed to a producing method of alight-emitting device having an emission region between an anode and acathode, the producing method comprising a medium disposing step ofdisposing a medium on the anode or the cathode; a porosity producingstep of making at least one of an anode side of the medium and a cathodeside thereof porous; a containing step of allowing materialcontributable to emission to be contained in a region in the vicinity ofa porous surface of the medium, so that the emission region is formed bythe medium and the material contributable to the emission; and adisposing step of disposing charge transport material on a poroussurface of the medium.

With this constitution, the material contributable to the emission iscollected to the porous surface of the emission region or the region inthe vicinity of the porous surface of the same and also the surface areaof he recombination region of the hole and the electron is enlarged,thus providing the light-emitting device with improved luminance.

A 55th aspect of the invention is directed to the producing method of alight-emitting device as set forth in the 53rd aspect of the invention,which comprises a disposing step of disposing charge transport materialon a porous surface of the emission region.

A 56th aspect of the invention is directed to the producing method of alight-emitting device as set forth in the 53rd aspect of the invention,which comprises a leveled layer forming step of forming a leveled layercomprising charge transport material on the emission region.

With the constitutions above in which the leveled layer is formed overthe emission region, the light-emitting device is provided having thecapabilities that leakage of current is prevented and also the injectionand transport of the hole or the electron can be performed with improvedefficiency and further, the leveled layer can permit the joint surfaceof the adjacent anode and cathode to be kept smooth.

A 57th aspect of the invention is directed to the producing method of alight-emitting device as set forth in the 53rd aspect of the invention,wherein the disposing step is a step of disposing a medium containingmaterial soluble in a specified solvent, and the porosity producing stepis a step of eluting the material from the solvent to thereby make themedium porous.

A 58th aspect of the invention is directed to a producing method of alight-emitting device having an emission region between an anode and acathode, the producing method comprising a medium disposing step ofdisposing a medium on the anode or the cathode; and a roughening step ofroughening a part of the medium.

A 59th aspect of the invention is directed to a producing method of alight-emitting device having an emission region between an anode and acathode, the producing method comprising a medium disposing step ofdisposing a medium on the anode or the cathode; a roughening step ofroughening at least one of an anode side of the medium and a cathodeside thereof, and a disposing step of disposing material contributableto emission on a roughened surface of the medium, so that the emissionregion is formed by the medium and the material contributable to theemission.

A 60th aspect of the invention is directed to a producing method of alight-emitting device having an emission region between an anode and acathode, the producing method comprising a medium disposing step ofdisposing a medium on the anode or the cathode; a roughening step ofroughening at least one of an anode side of the medium and a cathodeside thereof, and a containing step of allowing material contributableto emission to be contained in a region in the vicinity of a roughenedsurface of the medium, so that the emission region is formed by themedium and the material contributable to the emission.

With the constitutions above, the material contributable to the emissionis collected to the roughened surface of the emission region or theregion in the vicinity of the roughened surface of the same and also thesurface area of the recombination region of the hole and the electronwhere the material contributable to the emission is present is enlarged,thus providing the light-emitting device having the capability ofproducing improved luminance.

A 61st aspect of the invention is directed to the producing method of alight-emitting device as set forth in the 59th aspect of the invention,which comprises a leveled layer forming step of forming a leveled layercomprising charge transport material on the emission region.

With this constitution, the light-emitting device is provided having thecapabilities that leakage of current is prevented and also the injectionand transport of the hole or the electron can be performed with improvedefficiency and further, the joint surface of the adjacent anode andcathode can be kept smooth.

A 62nd aspect of the invention is directed to the producing method of alight-emitting device as set forth in the 59th aspect of the invention,wherein the roughening step is a step of roughening the emission regionby dry etching.

The dry etching enables the emission region to be roughened with ease.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of an organic light-emitting deviceaccording to an embodiment 1-1 of the present invention;

FIG. 2 shows schematic diagrams illustrating construction of an organiclight-emitting device according to an embodiment 1-2 of the presentinvention, FIG. 2(a) is a schematic conceptual diagram of the organiclight-emitting device and FIG. 2(b) is a sectional view taken along thearrowed line A—A of FIG. 2(a);

FIG. 3 shows schematic sectional views illustrating the producing methodof the organic light-emitting device according to the embodiment 1-2 ofthe present invention;

FIG. 4 shows schematic sectional views illustrating another example ofthe producing method of the organic light-emitting device according tothe embodiment 1-2 of the present invention;

FIG. 5 is a schematic diagram illustrating a distribution ofconcentration of an emission region of the organic light-emitting deviceaccording to the embodiment 1-2 of the present invention;

FIG. 6 is a schematic sectional view of an organic light-emitting deviceaccording to an embodiment 1-3 of the present invention;

FIG. 7 is a schematic sectional view of an organic light-emitting deviceaccording to an embodiment 1-4 of the present invention;

FIG. 8 is a schematic sectional view of an organic light-emitting deviceaccording to an embodiment 1-5 of the present invention;

FIG. 9 is a schematic sectional view of another example of the organiclight-emitting device according to the embodiment 1-5 of the presentinvention;

FIG. 10 is a schematic sectional view of yet another example of theorganic light-emitting device according to the embodiment 1-5 of thepresent invention;

FIG. 11 is an energy level diagram of the organic light-emitting deviceaccording to the embodiment 1-5 of the present invention;

FIG. 12 is an energy level diagram of the organic light-emitting deviceaccording to the embodiment 1-5 of the present invention;

FIG. 13 is an energy level diagram of the organic light-emitting deviceaccording to the embodiment 1-5 of the present invention;

FIG. 14 is an energy level diagram of the organic light-emitting deviceaccording to the embodiment 1-5 of the present invention;

FIG. 15 is a schematic sectional view of an organic light-emittingdevice according to an embodiment 2-1 of the present invention;

FIG. 16 shows schematic sectional views illustrating the producingmethod of the organic light-emitting device according to the embodiment2-1 of the present invention;

FIG. 17 is a schematic sectional view showing a variant of the organiclight-emitting device according to the embodiment 2-1 of the presentinvention;

FIG. 18 is a schematic sectional view of an organic light-emittingdevice according to the embodiment 2-2 of the present invention;

FIG. 19 shows schematic sectional views illustrating the producingmethod of the organic light-emitting device according to the embodiment2-2 of the present invention; and

FIG. 20 is a schematic sectional view showing an organic light-emittingdevice according to an embodiment 2-3 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of First InventiveGroup

In the following, the first inventive group of the present inventionwill be described with reference to the accompanying drawings.

While in the embodiments illustrated below (the same applies to thesecond inventive group), description is given on an organiclight-emitting device, the concept of the present invention above isapplicable not only to the organic light-emitting device but also to aninorganic light-emitting device wherein an emission region is formed,for example, by inorganic phosphor being dispersed in an organic binder.

Embodiment 1-1

FIG. 1 is a schematic sectional view of an organic light-emitting deviceaccording to an embodiment 1-1 of the present invention.

As shown in FIG. 1, an organic light-emitting device 10 comprises ananode 2 formed on a substrate 1, a cathode 4 arranged in opposition tothe anode 2, and an emission region 3 interposed between the anode 2 andthe cathode 4.

The emission region 3 comprises polymer 3A, luminous molecules 3G ofmaterial contributable to the emission, and charge transport materials3F. In FIG. 1, only one kind of luminous molecules is shown.

The luminous molecules 3G and the charge transport materials 3F aredistributed in concentration in a layer thickness direction of theemission region 3 (from the anode 1 to the cathode 4). Specifically, theconcentration of the luminous molecules 3G and the charge transportmaterials 3F are large at a side of the emission region 3 close to thecathode 4 (the upper side as viewed in the diagram) and are small at aside thereof close to the anode 2 (the lower side as viewed in thediagram). Preferably, the emission region 3 has a region in the layerthickness direction thereof where neither the luminous molecules 3G northe charge transport materials 3F are provided. In other words, it ispreferable that the emission region 3 has, at the side thereof close tothe anode 2, a region where neither the luminous molecules nor thecharge transport material exists but only the polymer 3A exists.

While it is described that the luminous molecules 3G and the chargetransport materials 3F are distributed in concentration in the layerthickness direction of the emission region, modification may be madesuch that only the luminous molecules 3G are distributed inconcentration in the layer thickness direction of the emission region 3and the charge transport materials 3F are uniformly distributed in thelayer thickness direction thereof.

Another modification may also be made of the organic light-emittingdevice, such that the emission region 3 comprises only the polymer 3Aand the luminous molecules 3G (not include the charge transportmaterials 3F) and the luminous molecules 3G are distributed inconcentration in the layer thickness direction.

An emission mechanism of the organic light-emitting device of thepresent invention is as follows. In the organic light-emitting device 10shown in FIG. 1, when a positive voltage is applied to the anode 2 and anegative voltage is applied to the cathode 4, the hole is injected intothe emission region 3 from the anode 2 and the electron is injected intothe emission region 3 from the cathode 4. Then, the injected hole flowsto the cathode 4 and the injected electron flows to the anode 2. Thehole and the electron are recombined in the emission region 3, inresponse to which fluorescence or phosphorescence is emitted from theluminous molecules 3G in the emission region 3.

The following points can be cited as major factors for determiningcurrent efficiency of the emission (emission efficiency for the injectedcurrent) include:

(1) Efficiency of recombination of the hole and electron for theinjected current;

(2) Efficiency of generation of the excitons of the luminous moleculessequent from the recombination; and

(3) Efficiency of generation of luminous quantum from the excitons ofthe luminous molecules;

Of the factors above, (2) and (3) are practically determined by theluminous molecules' properties themselves.

On the other hand, the efficiency of recombination of the hole andelectron of (1) is most influenced by the balance between the hole andthe electron. If the hole and the electron are badly balanced, even ifthey are injected from the electrode, excess carriers reach the oppositeelectrode without being recombined in the emission region, resulting inwasteful currents that do not contribute to the emission.

If the mobility of the carriers in the emission region is enhanced, thenthe hole and the electron flow in a balanced manner and the luminousefficiency is improved. Specifically, it is preferable that the mobilityof the hole is 1×10⁻⁷ cm²/V·s or more and the mobility of the electronis 5×10⁻⁸ cm²/V·s or more.

When viewing from the emission mechanism mentioned above, in the casewhere the emission region includes a region of high holetransportability and a region of high electron transportability withrespect to the layer thickness direction, or specifically, in the casewhere the hole transportability is high on the anode side of theemission region and the electron transportability is high on the cathodeside of the same, the hole and the electron injected from the anode andthe cathode respectively are locally recombined in the vicinity of theinterface of the both regions.

Thus, when the luminous molecules 3G and the charge transport materials3F are distributed in concentration in the layer thickness direction, asshown in FIG. 1, or preferably, when the emission region 3 includes aregion in which neither the luminous molecules 3G nor the chargetransport materials 3F exists, a region different in carriertransportability is formed in the emission region 3, so that therecombination efficiency of the above-noted (1) is further improved andthe emission efficiency is also improved.

Embodiment 1-2

FIG. 2 shows schematic diagrams illustrating construction of an organiclight-emitting device according to an embodiment 1-2 of the presentinvention. FIG. 2(a) is a schematic conceptual diagram of the organiclight-emitting device and FIG. 2(b) is a sectional view taken along thearrowed line A—A of FIG. 2(a).

As shown in FIG. 2, an organic light-emitting device 20 is a simplematrix type one comprising anodes 22 formed on a substrate 21 in astriped form, an emission region 23 formed on the anodes 22, andcathodes 24 formed on the emission region 23 in a striped form to extendorthogonal to the anodes 22.

The substrate 21 may be made of any material capable of supporting theorganic light-emitting device 20 of the present invention. A transparentsubstrate made of glass or resin film such as polycarbonate, polymethylmethacrylate, and polyethylene terephthalate, or an opaque substratemade of silicon can be used as the substrate.

At least either of the anodes 22 and the cathodes 24 must be transparentor translucent to take out the light generated from the emission region23 through the either or both of the electrodes.

While the transparent electrodes made of for example indium tin oxide(ITO) or tin oxide are often used as the anodes 22 in general, metallicelectrodes made of, for example, Ni, Au, Pt, Pd, may be used. As for theITO film, the deposition processes, such as a sputtering, an electronbeam evaporation, an ion plating, is adopted, for the sake of improvingthe transparency or reducing the resistivity. The layer thickness isdetermined from a required sheet resistance and a required visible lighttransmittance, but since the organic light-emitting device is relativelylarge in drive current density, the film is often used with thethickness of 1,000 or more, in order to reduce the sheet resistance.

Laminated electrodes of metal, such as Al, Ag and Au, alloy composed ofmetal of low in work function and metal of relatively large in workfunction and stable, such as MgAg alloy and AlLi alloy, and alloycomposed of metal of low in work function and metal of high in workfunction, such as Li/Al and LiF/Al, can be used as the cathodes 24.These cathodes are preferably formed in the evaporation or thesputtering.

The anodes 22 and the cathodes 24 are the electrodes extendingorthogonal to each other in the striped form. When a forward voltage isapplied to selected anodes and cathodes, the emission region emits lightwith luminance corresponding to the applied voltage at the intersectionpoints of the both of the electrodes.

While in this embodiment, the substrate 21, the anodes 22, the emissionregion 23 and the cathodes 24 are laminated in order from the bottom,they are not necessarily required to be laminated in this order. Theorder of lamination of these, from bottom to top, may be the substrate21, the cathodes 24, the emission region 23 and the anodes 22.

If only the electrodes on the substrate 21 side or the anodes 22 aretransparent and the cathodes 24 are opaque, then the substrate 21 isrequired to be transparent in order to take out the light generated.

Next, description on the emission region 23 will be given. The emissionregion 23 comprises polymer 23A, luminous molecules (Red) 23R, luminousmolecules (Green) 23G and luminous molecules (Blue) 23B. The polymer 23Ais seriated in an in-plane direction of the emission region 23, and anumber of luminophors 23R, 23G, 23B are adjacently arranged in thedirection parallel to the cathodes 24 and the anodes 22. The luminophors23R, 23G, 23B are so distributed in density as to substantiallycontinuously reduce from around the center of the emission region to theperiphery in the direction parallel to the cathodes 24 and the anodes22.

Now, description on the producing method of the organic light-emittingdevice according to the embodiment 1-2 of the present invention will begiven. FIG. 3 shows schematic sectional views illustrating the producingmethod of the organic light-emitting device according to the embodiment1-2 of the present invention.

(1) First, the anodes 22 made of ITO or equivalent are formed on thesubstrate 21 by the deposition method such as the sputtering, theelectron beam evaporation, and the ion plating, as shown in FIG. 3(a).

(2) Then, the anodes 22 are patterned into a desired pattern (thestriped form in this case) as shown in FIG. 3(b). For example, in thecase of the ITO electrode, photo resist used is patterned by use of acommon photo lithography and then is etched by hydriodic acid orequivalent.

(3) Then, the polymer 23A of e.g. poly-N-vinylcarbazol is deposited onthe anodes 22, as shown in FIG. 3(c). Though the deposition may beperformed by any of the methods, such as the evaporation, thesputtering, and the method of application, it is performed mainly by themethod of application. To be concrete, the solution ofpoly-N-vinylcarbazol dissolved in solvent such as toluene or chloroformis applied to the substrate 1 by the spin coat method or equivalent. Thelayer thickness of the polymer 3A is preferably in the range of about500 to about 3,000, though it is not limited to any particularthickness.

(4) Then, after the polymer 23A is deposited on the anodes, the luminousmolecules having a desired luminous color is made to penetrate into adesired location, as shown in FIG. 3(d). Specifically, when a RGB fullcolor panel is produced, the solution of the red luminous molecules 23Rdissolved in the solvent is first discharged to drop on the red-colorelectrodes (every two electrodes) of the striped anodes 22 formed of ITOin the ink-jet method using the ink heads 27, so as to penetrate intothem.

(5) Then, the solution of the green luminous molecules 23G is dischargedonto the striped green-color anodes 22 by use of the ink heads 27 in thesame manner, as shown in FIG. 3(e).

(6) Then, the solution of the blue luminous molecules 23B is dischargedonto the blue-color anodes 22. in the same manner, as shown in FIG.3(f). It is to be noted that any particular limitation is not imposed onthe dropping order of the red, green and blue luminous molecules, andthe luminous molecules may be dropped in any selected order. Theluminous molecules are preferably heat-treated, after dropping. The heattreatment can accelerate the penetration of the luminous molecules 23R,23G, 23B into the polymer 23A. For further acceleration of thepenetration of the luminous molecules into the polymer 23A, it ispreferable that a polymer-23A-soluble liquid is used as the solvent todissolve the luminous molecules.

(7) Then, the striped cathodes 24 are formed to extend orthogonal to thestriped anodes 22, as shown in FIG. 3(g). The deposition is performed inthe evaporation method or the sputtering using the evaporation maskhaving a desired pattern.

While in the embodiment 1-2, the luminous molecules are penetrated intothe polymer, the charge transport material as well as the luminousmolecules may be penetrated into the polymer. Alternatively, theluminous molecules may be penetrated into the polymer in which thecharge transport material is dispersed.

The method above allows the luminous molecules 23R, 23G and 23B topenetrate into the polymer in the ink-jet method, so that the need ofthe application of the polymer solution of high viscosity in the ink-jetmethod can be eliminated. Therefore, the luminous molecules can beapplied without the nozzles of the ink jet being plugged, thus enablingthe molecules to be formed into fine patterns.

Referring now to FIG. 5, description will be given on the configurationof the emission region of the organic light-emitting device produced inthe producing method mentioned above. FIG. 5 is a schematic diagramillustrating a distribution of concentration of an emission region ofthe organic light-emitting device according to the embodiment 1-2 of thepresent invention.

The luminous molecules (Red) 23R, the luminous molecules (Green) 23G andthe luminous molecules (Blue) 23B are dispersed over the striped anodes22 in the in-plane direction of the emission region 23 (in the directionparallel to the electrodes), and the distribution of concentration ofeach luminous molecule 23R, 23G and 23B becomes the maximum at asubstantially center point over the respective anode 22 and graduallyreduces toward the both ends of the each anode 22, as shown in FIG. 5.

This constitution enables the luminous molecules 23R, 23G, 23B in thevicinity of their boundaries to be small in concentration. Therefore,the luminous molecules 23R, 23G, 23B are prevented from being mixed in,thus providing little color mixture and thus producing an excellent fullcolor display performance.

Further, the luminous molecules 23R, 23G, 23B are penetrated into thepolymer 23A in the ink-jet method using the ink-jets 27, so that theconcentration of the luminance molecules 23R, 23G, 23B in the emissionregion 23 becomes larger on the cathode 24 side than on the anode 22side.

Consequently, the organic light-emitting device of the embodiment 1-2can provide increased recombination efficiency of the electron and thehole, to produce improved luminous efficiency, as is the case with theembodiment 1-1 above.

FIG. 4 shows schematic sectional views illustrating another example ofthe producing method of the organic light-emitting device according tothe embodiment 1-2 of the present invention.

The procedures shown up to FIG. 4(c) are the same as those of FIG. 3that the polymer 3A is formed over the substrate 1 on which the anode 2is formed.

Then, the luminous molecules 3R, 3G, 3B are penetrated in the polymer 3Ain the following manner.

First, after a mask 8 having opening formed only on the red-colorelectrode of the striped anodes 2 of ITO is set on the substrate 1,steaming is performed by use of solution of red luminous moleculesdissolved in the solvent, as shown in FIG. 4(d), so that the redluminous molecules 3R are penetrated into the polymer at the desiredlocations.

Sequentially, the green luminous molecules 3G and the blue luminousmolecules 3B are penetrated in the same manner, as shown in FIG. 4(e),(f). It is to be noted that any particular limitation is not imposed onthe steaming order of the red, green and blue luminous molecules, andthe luminous molecules may be steamed in any selected order. Preferably,the luminous molecules are heat-treated after steamed. Theheat-treatment can accelerate the penetration of the luminous molecules3B-3D into the polymer 3A. For further acceleration of the penetrationof the luminous molecules into the polymer 3A, it is preferable that thepolymer-3A-soluble liquid is used as the solvent to dissolve theluminous molecules.

Finally, the striped cathodes 4 are formed to extend orthogonal to thestriped anodes 2 in the same manner as in FIG. 3.

While in the embodiment above, the luminous molecules are penetratedinto the polymer, the charge transport material as well as the luminousmolecules may be penetrated into the polymer. Alternatively, theluminous molecules may be penetrated into the polymer in which thecharge transport material is dispersed.

Also, the method of penetrating the luminous molecules into the polymerin the printing method can be cited as another example of the producingmethod of the organic light-emitting device according to the presentinvention.

Specifically, in place of the luminous molecules 3R, 3G, 3B beingpenetrated into the polymer 3A in the steaming in FIG. 4(d)-(f),solution of the luminous molecules is applied to and penetrated into thepolymer 3A by use of an offset printing method or a screen printingmethod.

In this variant as well, the luminous molecules are preferablyheat-treated after printed, as is the case with the example noted above.Further, the polymer-3A-soluble liquid is used as the solvent todissolve the luminous molecules. Instead of the luminous molecules beingpenetrated into the polymer, the charge transport material as well asthe luminous molecules may be penetrated into the polymer.Alternatively, the luminous molecules may be penetrated into the polymerin which the charge transport material is dispersed.

Embodiment 1-3

FIG. 6 is a schematic sectional view of an organic light-emitting deviceaccording to an embodiment 1-3 of the present invention.

The embodiment 1-3 differs from the embodiment 1-2 in that in additionto the luminous molecules 23R, 23G, 23B, the charge transport material23E are presented in the emission region 23. Here, the polymer 23A andthe charge transport material 23E are seriated in the in-plane directionof the emission region 23. In other words, the charge transport material23E is uniformly dispersed in the polymer 23A. The luminous molecules23R, 23G, 23B are dispersed over the striped anodes 22, respectively, asis the case with the embodiment 1-2.

Embodiment 1-4

FIG. 7 is a schematic sectional view of an organic light-emitting deviceaccording to an embodiment 1-4 of the present invention.

FIG. 7 differs from FIG. 6 in that the charge transport material 23E arenot seriated in the in-plane direction of the emission region 23, butare distributed in concentration in the in-plane direction, as is thecase with the luminous molecules 23R, 23G and 23B. Specifically, thecharge transport material 23E are present in large concentration in aregion where the luminous molecules 23R, 23G, 23B are large inconcentration.

Commonalities among Embodiments 1-2 to 1-4

Polymer having charge transport capabilities (charge transport polymer)is preferably used as the polymeric material. Among others, polymerhaving hole transport capabilities (hole transport polymer) ispreferable. Preferably, the hole transport polymer has the mobility ofcarrier of 1×10⁻⁷ cm²/V·s or more. Particularly preferable ispoly-N-vinylcarbazol.

When the hole transport polymer is used, the electron transport materialis preferably used as the charge transport material. Further, it ispreferable that the electron transport material has the mobility of thecarrier of 5×10⁻⁸ cm²/V·s or more. Particularly preferable are oxazolederivative, oxadiazole derivative, triazole derivative, pyrazinederivative, aldazine derivative, quinolinol complex and derivativethereof. A content of the electron transport material to the polymer ispreferably 30-120 weight %. With the electron transport material contentof less than 30 weight %, the electron transportability is notsufficient, while on the other hand, with the electron transportmaterial content of more than 120 weight %, the dispersibility into thepolymer deteriorates.

Fluophor or phosphor that exhibits luminescence in response to therecombination of the hole and electron may be used as the luminousmolecules. The materials that emit particularly strong fluonescence orphosphonescence, which may be used, include coloring matters or laserdyes, such as cyanine dye, merocyanine dye, styrylic dye, anthracenederivative, porphyrin derivative, phthalocyanine derivative, coumarin,DCM and Nile red. Preferably used as the luminous molecule is thematerial having ionization potential of the luminous molecule smallerthan ionization potential of the hole transport polymer and alsoelectron affinity of the luminous molecule larger than electron affinityof the electron transport material.

Embodiment 1-5

FIGS. 8-10 are schematic sectional views of the organic light-emittingdevice according to an embodiment 1-5 of the present invention. In FIGS.8-10, 25 designates a hole injection layer, 26 designates an electroninjection layer, 23G designates the luminous molecules, 23H designateshole transport material, and 23I designates electron transport material.

The hole injection layer 25 is inserted for the purpose of subservingthe injection of the hole from the anode 22 into the emission region 23.Preferably, the material used for the hole injection layer 25 has therelation among the ionization potential of the hole injection layer(Ip(h)), the ionization potential of the polymer (Ip(p)) and theionization potential of the anode or the work function (Ip(a)) of theanode being Ip(a)<Ip(h)<Ip(p). It is particularly preferable that thehole injection layer comprises at least one material of polyanilinederivative, polythiophene derivative and amorphous carbon.

The electron injection layer 26 is inserted for the purpose ofsubserving the injection of the electron from the cathode 24 into theemission region 23. Desirably, the material used for the electroninjection layer 26 has the electron affinity or work function smallerthan the work function of the cathode. It is particularly preferablethat the electron injection layer comprises at least one material ofdilithium phthalocyanine, disodium phthalocyanine and organic boroncomplex compound.

The hole transport material 23H is introduced for the purpose ofsubserving the injection of the hole from the anode 22 into the emissionregion 23, as is the case with the hole injection layer. However,differently from the hole injection layer 25, the hole transportmaterial is not inserted in between the anode 22 and the emission region23 in the form of a layer, but is directly dispersed in the emissionregion.

Preferably, the material used for the hole transport material 23H hasthe ionization potential smaller than the ionization potential of thepolymer. A content of the hole transport material to the polymer ispreferably 10-120 weight %. With the hole transport material content ofless than 10 weight %, the hole cannot be injected fully, while on theother hand, with the hole transport material content of more than 120weight %, the dispersibility into the polymer deteriorates.

The effects produced by the introduction of the hole injection layer 25,the electron injection layer 26 and the hole transport material 23H willbe described with reference to the related diagrams. FIGS. 11-14 areenergy level diagrams of the organic light-emitting device according tothe present invention.

FIG. 11 shows an energy level diagram and an operation mechanism of anorganic light-emitting device having the structure of anode/emissionregion (hole transport polymer+electron transport material+luminousmolecules (luminescent material))/cathode. FIG. 12 shows an energy leveldiagram and an operation mechanism of an organic light-emitting devicehaving the structure of anode/hole injection layer/emission region (holetransport polymer+electron transport material+luminous molecule/cathode.As already noted, when a voltage is applied to the organiclight-emitting device, the hole is injected from the anode into theemission region and the electron is injected from the cathode into theemission region. In more detail, as shown in FIG. 11, the both carriersare injected into the material of smaller injection barrier. In otherwords, the hole is injected into the hole transport polymer in theemission region, and the electron is injected into the electrontransport material in the emission region. It should be noted that thesmaller the injection barrier for the both carriers (hole and electron)become, the more the injection of the carriers facilitates and the morethe driving voltage reduces. This reduction of the driving voltage canprovide improved power efficiency for emission (emitting efficiency forinput power) even when the current efficiency is identical. For example,when the hole injection layer having the ionization potential betweenthe anode and the hole transport polymer is inserted, the hole injectionbarrier is relaxed, as shown in FIG. 12, and the driving voltage canalso be lowered. Further, when the hole injection barrier is greaterthan the electron injection barrier, as shown in FIG. 11, the holeinjection barrier is lowered so that an improved balance between theinjection rate of the hole and the injection rate of the electron isproduced, and as such can allow the current efficiency to be expectablyimproved by the aforesaid effects. FIG. 13 shows an energy level diagramof an organic light-emitting device having the structure ofanode/emission region (hole transport polymer+electron transportmaterial+luminous molecules)/electron injection layer/cathode. As is thecase with the hole injection barrier, the electron injection barrier canalso be lowered by inserting the electron injection layer smaller inelectron affinity than the cathode, as shown in FIG. 13, thus producingreduction in driving voltage and improvement in luminous efficiency.FIG. 14 shows an energy level diagram of an organic light-emittingdevice having the structure of anode/emission region (hole transportpolymer+hole transport material+electron transport material+luminousmolecules)/cathode. In this case, since the ionization potential of thehole transport material is smaller than that of the hole transportpolymer, the hole is directly injected into the hole transport materialin the emission region from the anode, as shown in the diagram, so thatthe injection barrier is lowered, as compared with the case of the holebeing injected into the hole transport polymer. Hence, as is the casewith the structure of the hole injection layer being inserted, thedriving voltage can be reduced and at the same time the currentefficiency can be expectedly improved.

Of course, the above-noted structures may be combined to provide thestructure wherein both of the hole injection layer and the electroninjection layer are inserted; the structure wherein the emission regioncomprises the hole transport polymer+hole transport material+electrontransport material+luminous molecules and further the electron injectionlayer is inserted; or the structure wherein the luminous molecules andthe charge transport material are distributed in concentration in thelayer thickness direction of the emission region.

While in the above-mentioned embodiments 1-1 to 1-5, examples of thesimple matrix organic light-emitting device are shown, modification maybe made, such as, for example, forming the light emitting devicestructured as mentioned above on the thin film transistor to produce anactive matrix display panel.

Now, experimental examples based on the embodiments mentioned above willbe described in further detail.

EXPERIMENTAL EXAMPLE 1

The organic light-emitting device was produced as mentioned below, inaccordance with the procedures of FIG. 3 illustrated in the aforesaidEmbodiment 1-1.

A glass substrate having thickness of 0.7 mm was used as the substrate 1and ITO was deposited thereon in the form of the anode 2 by thesputtering method. The ITO was deposited to have thickness of about1,000 and the sheet resistance was set at about 150Ω/□. The ITO waspatterned in the striped form having width of 300 μm by use of photolithography.

Then, after the substrate was washed and subjected to oxygen plasmatreatment, poly-N-vinylcarbazol (PVK)(molecular weight of about 28,000)was deposited thereon as the polymer 3A. The PVK is the hole transportpolymer and the mobility of the carriers is about 2×10⁻⁶ cm²/V·s. Thedeposition was performed in the spin coat method, using the solution inwhich 300 mg of PVK was dissolved in 30 ml of toluene. The spin coat wasperformed with spin in a closed state in the conditions of 500 rpm/10sec. and of 1,000 rpm/30 sec.

Then, the PVK was heat-treated at 110° C. for 1 minute by use of a hotplate. It was about 1,000 in layer thickness.

Then, the luminous molecules were dropped on the ITO electrodes atdesired locations by use of a commercially available ink-jet printer, toform the emission region. Nile red was used as red luminous molecules(3R), coumarin 6 was used as green luminous molecules (3G), and coumarin47 was used as blue luminous molecules (3B). The respective luminousmolecules were discharged from the ink head 7 in the form of solution inwhich 1 mg of luminous molecules were dissolved 10 ml of chloroform.Every time the luminous molecules were dropped, they were heat-treatedat 110° C. for 1 minute by use of the hot plate.

Finally, Li/Al laminated electrodes were deposited as the cathodes 4 bythe vacuum evaporation method. The deposition was performed under thedegree of vacuum of about 5×10⁻⁶ Torr. First, Li was allowed toevaporate by 10 at a rate of about 0.5/sec. and then Al was allowed toevaporate by 1,500 at a rate of about 30/sec. The cathodes was formedinto the striped form orthogonal to the anodes 2 by use of theevaporation mask and having the width of 300 μm.

The energy levels of the respective materials are as follows. Theionization potential of the ITO is 4.9 eV, the ionization potential ofthe PVK is 5.6 eV, the electron affinity is 2.0 eV, the ionizationpotential of Nile red is 5.3 eV, the electron affinity is 3.5 eV, theionization potential of coumarin 6 is 5.4 eV, the electron affinity is2.9 eV, the ionization potential of coumarin 47 is 5.4 eV, and theelectron affinity is 2.5 eV. The work function of Li is 2.9 eV and thework function of Al is 4.3 eV.

When an elemental analysis of the region where the coumarin 6 wasdropped was made with respect to the layer thickness direction, in orderto examine the distribution of concentration of the luminous moleculesin the emission region 3, it was found that the quantity of sulfurcontained only in the coumarin 6 gradually decreased from the cathodeside toward the anode side and there were no coumarin 6 left in thevicinity of the anode.

In the organic light-emitting device thus produced, when a forwardvoltage of the order of 10V was applied across the selected stripedanode and cathode, the part (critical area) sandwiched between the bothelectrodes emitted light brightly in the respective colors correspondingto the luminous molecules (Nile red: red, coumarin 6: green, andcoumarin 47: blue). Thus, the simple matrix display capable of emittinglight in the desired colors at desired locations (critical areas) wasproduced.

The current efficiency of each luminescent color (cd/A), the drivingvoltage at a luminance of 100 cd/m² and the power efficiency (lm/W) at aluminance of 100 cd/m² are shown in TABLE 1.

TABLE 1 Driving voltage Power efficiency Current efficiency (cd/A) (at100 cd/m²)(V) (at 100 ed/m²)(lm/W) Red Green Blue Red Green Blue RedGreen Blue Experimental 1.5 3.0 1.7 12.0 11.0 12.0 0.4 0.9 0.4 Example 1Experimental 3.0 6.0 3.4 10.4 9.0 10.0 0.9 2.1 1.1 Example 2Experimental 3.3 7.2 4.0 9.2 8.0 9.0 1.1 2.8 1.4 Example 3 Experimental1.8 4.1 2.0 10.5 9.2 10.3 0.5 1.4 0.6 Example 4 Experimental 1.9 4.2 2.010.5 9.0 10.0 0.6 1.5 0.6 Example 5 Experimental 1.9 4.2 2.1 10.4 9.010.1 0.6 1.5 0.7 Example 6 Experimental 1.8 4.1 2.0 10.5 9.0 10.0 0.51.4 0.6 Example 7 Experimental 1.7 4.0 2.1 10.2 8.8 9.9 0.5 1.4 0.7Example 8 Experimental 1.8 4.5 2.2 10.3 8.9 9.9 0.5 1.6 0.7 Example 9Experimental 3.5 7.1 3.8 9.0 7.6 8.7 1.2 2.9 1.4 Example 10 Experimental1.6 3.2 1.5 12.0 11.0 12.1 0.4 0.9 0.4 Example 11 Experimental 3.0 6.13.2 10.4 9.0 10.1 0.9 2.1 1.0 Example 12 Experimental 3.4 7.0 4.0 9.28.0 9.1 1.2 2.7 1.4 Example 13 Experimental 1.5 3.1 1.6 10.5 9.2 10.20.4 1.1 0.5 Example 14 Experimental 3.0 6.1 3.0 10.5 9.0 10.0 0.9 2.10.9 Example 15 Experimental 3.5 7.2 3.9 10.4 9.0 10.1 1.1 2.5 1.2Example 16

EXPERIMENTAL EXAMPLE 2

In Experimental example 1, in place of the PVK being deposited as thepolymer 3A, the PVK in which 2-(4-biphenyl)-5-(4-tertbuthylphenyl)-1,3,4-oxadiazole (PBD) was dispersed. The PBD is theelectron transport material and the mobility of the carriers is about2×10⁻⁶ cm²/V·s. The ionization potential is 6.1 eV and the electronaffinity is 2.4 eV. The deposition was performed in the same conditionsas those of the experimental example 1 by the spin coat method, usingthe solution in which 300 mg of PVK and 180 mg of PBD are dissolved in30 ml of solvent in which toluene and chloroform were mixed in theproportion 1:1.

The properties of this device are shown in TABLE 1.

EXPERIMENTAL EXAMPLE 3

In Experimental example 1, in place of the luminous molecules beingdropped, the mixed solution of the luminous molecules and the PBD(electron transport material) was dropped.

Specifically, the solution in which 1 mg of Nile red+100 mg of PBD, 1 mgof coumarin 6+100 mg of PBD, and 1 mg of coumarin 47+100 mg of PBD wererespectively dissolved in 30 ml of solvent in which toluene andchloroform were mixed in the proportion 1:1 was dropped on the PVK bythe ink jet method.

The properties of this device are shown in TABLE 1.

EXPERIMENTAL EXAMPLE 4

In Experimental example 1, the hole injection layer was inserted inbetween the anode and the emission region.

In short, the device was structured, as shown in FIG. 8. The holeinjection layer was formed by the spin coat method using a commerciallyavailable polythiophene derivative, to have layer thickness of 150,before the deposition of the PVK. The ionization potential of thepolythiophene derivative used here is 5.3 eV.

The properties of this device are shown in TABLE 1.

EXPERIMENTAL EXAMPLE 5

As a substitution for the polythiophene derivative as the hole injectionlayer of the experimental example 4, a commercially availablepolyaniline derivative that exhibits equivalent ionization potential tothe above-noted polythiophene derivative was used. The deposition of thepolyaniline derivative was performed in the same manner as in theexperimental example 2, to have layer thickness of 150.

The properties of this device are shown in TABLE 1.

EXPERIMENTAL EXAMPLE 6

As a substitution for the polythiophene derivative as the hole injectionlayer of the experimental example 4, amorphous carbon was used. Theamorphous carbon was formed to have layer thickness of 100 by thesputtering method. The ionization potential of the amorphous carbon is5.2 eV.

The properties of this device are shown in TABLE 1.

EXPERIMENTAL EXAMPLE 7

In Experimental example 1, the electron injection layer was inserted inbetween the emission region and the cathode.

In short, the device was structured, as shown in FIG. 9. Dilithiumphthalocyanine was used and deposited as the electron injection layer bythe vacuum evaporation method after the luminous molecules were droppedover the PVK. Sequentially, Al was deposited as the cathode. Theelectron injection layer and the cathode were formed in the manner thatafter dilithium phthalocyanine was deposited 10 at a rate of about0.3/sec., Al was deposited 1,500 at a rate of about 30/sec. The electronaffinity of dilithium phthalocyanine is 3.0 eV.

The properties of this device are shown in TABLE 1.

EXPERIMENTAL EXAMPLE 8

As a substitution for the dilithium phthalocyanine as the electroninjection layer of the experimental example 7, disodium phthalocyaninethat exhibits equivalent electron affinity thereto was used. Thedeposition of the disodium phthalocyanine was performed in the samemanner as in the experimental example 7, to have layer thickness of 10.

The properties of this device are shown in TABLE 1.

EXPERIMENTAL EXAMPLE 9

As a substitution for the dilithium phthalocyanine as the electroninjection layer of the experimental example 7, 4,4,8,8-tetrakis(1H-pyrazole-1-yl) pyrazabole was used. The deposition of the4,4,8,8-tetrakis (1H-pyrazole-1-yl) pyrazabole was performed in the samemanner as in the experimental example 7, to have layer thickness of 10.The electron affinity of the 4,4,8,8-tetrakis (1H-pyrazole-1-yl)pyrazabole is 2.3 eV

The properties of this device are shown in TABLE 1.

EXPERIMENTAL EXAMPLE 10

In the experimental example 3, in place of PVK being deposited as thepolymer 3A, the PVK in which N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD) is dispersed as thehole transport material. In short, the device shown in FIG. 10 wasproduced. The ionization potential of TPD is 5.4 eV. The deposition wasperformed in the same conditions as those of the experimental example 1by the spin coat method, using the solution in which 300 mg of PVK and180 mg of PBD were dissolved in 30 ml of mixed solvent in which tolueneand chloroform were mixed in the proportion 1:1.

The properties of this device are shown in TABLE 1.

EXPERIMENTAL EXAMPLE 11

In accordance with the procedure of FIG. 4, the organic light-emittingdevice was produced. After the procedures until FIG. 4(c) were performedin the same manner as in the experimental example 1, the luminousmolecules are penetrated into the polymer 3A by steaming, to form theemission region. The luminous molecules used Nile red, coumarin 6 andcoumarin 47, as is the case with the experimental example 1. Thesteaming was performed in the following manner. First, after the maskhaving the openings at portions corresponding to the red-colorelectrodes of the striped anodes 2 formed of ITO was set on thesubstrate, the polymer was subjected to the steam generated by heatingthe solution in which 10 mg of Nile red was dissolved in 10 ml oftoluene. Further, it was heat-treated at 110° C. for 1 minute by use ofa hot plate. Thus, the Nile red was penetrated into the substrate at thedesired positions thereof. Sequentially, after the mask was shifted inposition so that the openings were over the green-color electrodes, thepolymer was subjected to the steam generated by heating the solution inwhich 10 mg of coumarin 6 was dissolved in 10 ml of toluene and furtherwas heat-treated at 110° C. for 1 minute. Sequentially, after the maskwas shifted in position in the same manner, the polymer was treated bythe steaming using the solution in which 10 mg of coumarin 47 wasdissolved in 10 ml of toluene and further was heat-treated at 110° C.for 1 minute. Finally, the Li/Al laminated electrodes were deposited asthe cathodes 24 in the vacuum evaporation method in the same manner asin the experimental example 1.

The properties of this device are shown in TABLE 1.

EXPERIMENTAL EXAMPLE 12

In the experimental example 11, in place of PVK being deposited as thepolymer 3A, the PVK in which 2-(4-biphenyl)-5-(4-tertbuthylphenyl)-1,3,4-oxadiazole (PBD) was dispersed was deposited. Thedeposition was performed in the same conditions as those of theexperimental example 1 by the spin coat method, using the solution inwhich 300 mg of PVK and 180 mg of PBD were dissolved in 30 ml of mixedsolvent in which toluene and chloroform were mixed in the proportion1:1.

The properties of this device are shown in TABLE 1.

EXPERIMENTAL EXAMPLE 13

In the experimental example 11, in place of the luminous molecules beingsteamed, the mixed solution of the luminous molecules and the PBD wassteamed.

Specifically, the solution in which 1 mg of Nile red+100 mg of PBD, 1 mgof coumarin 6+100 mg of PBD, and 1 mg of coumarin 47+100 mg of PBD wererespectively dissolved in 30 ml of mixed solvent in which toluene andchloroform were mixed in the proportion 1:1 was used and steamed on thePVK.

The properties of this device are shown in TABLE 1.

EXPERIMENTAL EXAMPLE 14

In the experimental example 1, in place of the luminous molecules beingdropped, the luminous molecules were penetrated in the printing method.After the PVK was deposited on the substrate in the same procedure as inthe experimental example 1, the solution in which 1 mg of Nile red wasdissolved in 10 mg of toluene was applied to the desired ITO electrodesin the screen printing method and then was heat-treated at 10° C. for 1minute by use of the hot plate. Likewise, the solution in which 1 mg ofcoumarin 6 and coumarin 47 were dissolved in 10 ml of toluene wasapplied to the desired ITO electrodes in the screen printing method andthen was heat-treated at 110° C. for 1 minute by use of the hot plate.Finally, the Li/Al laminated electrodes were deposited as the cathodes24 in the vacuum evaporation method in the same manner as in theexperimental example 1.

The properties of this device are shown in TABLE 1.

EXPERIMENTAL EXAMPLE 15

In the experimental example 14, in place of PVK being deposited as thepolymer 3A, the PVK in which 2-(4-biphenyl)-5-(4-tertbuthylphenyl)-1,3,4-oxadiazole (PBD) was dispersed was deposited. Thedeposition was performed in the same conditions as those of theexperimental example 1 by the spin coat method, using the solution inwhich 300 mg of PVK and 180 mg of PBD were dissolved in 30 ml of mixedsolvent in which toluene and chloroform were mixed in the proportion1:1.

The properties of this device are shown in TABLE 1.

EXPERIMENTAL EXAMPLE 16

In the experimental example 14, in place of the luminous molecules beingapplied in the screen printing method, the mixed solution of theluminous molecules and the PBD was applied in the screen printingmethod. Specifically, the solution in which 1 mg of Nile red+100 mg ofPBD, 1 mg of coumarin 6+100 mg of PBD, and 1 mg of coumarin 47+100 mg ofPBD were respectively dissolved in 30 ml of mixed solvent in whichtoluene and chloroform were mixed in the proportion 1:1 was applied ontothe PVK in the screen printing method.

The properties of this device are shown in TABLE 1.

Embodiments of Second Inventive Group

The light-emitting device of the second inventive group is characterizedin that it comprises the emission region provided between the anode andthe cathode and comprising material contributable to the emission andalso comprises a collecting means, provided between the anode and thecathode, for collecting the material contributable to the emission intoa specific region. To be more concrete, the light-emitting devicecomprises the emission region provided between the anode and the cathodeand comprising material contributable to the emission; a porous orroughened region between the anode and the cathode; and materialcontributable to the emission which is arranged on as well as in thevicinity of a front surface of the porous or roughened region.

As mentioned above, the provision of the porous or roughened region canallow the material contributable to the emission to be collected to aspecific region (on or in the vicinity of the front surface of theporous or roughened region) and also can enlarge a surface area of thehole-and-electron recombination region where the material contributableto the emission is present. This can produce the emission with highluminance.

The application of the light-emitting device thus constructed to adisplay or a lighting device can produce the display or lighting devicehaving high luminance performance.

In the following, the embodiment 2-1 illustrates the light-emittingdevice having the structure in which the emission region is made porous.The embodiment 2-2 illustrates the structure in which the emissionregion is roughened. Further, the embodiment 2-3 illustrates thestructure in which the charge transport region is made porous or isroughened.

Embodiment 2-1

FIG. 15 is a schematic sectional view of an organic light-emittingdevice according to an embodiment 2-1 of the present invention.

As shown in FIG. 15, an organic light-emitting device 100 comprises ananode 105 formed on a substrate (not shown), a cathode 101 arranged inopposition to the anode 105, an emission region 109 arranged between theanode 105 and the cathode 101, and a leveled layer 102 arranged betweenthe cathode 101 and the emission region 109.

The emission region 109 comprises an organic layer 104 which is madeporous on the cathode 101 side thereof, and luminance molecules 103arranged on a front surface of the organic layer 104 thus made porous.

Further, a leveled layer 102 comprising charge transport material isformed on the front surface of the organic layer 104 and the cathode 101is laminated on the leveled layer 102.

This constitution, in which the luminous molecules 103 are collected onthe front surface of the organic layer 104 as was made porous to enlargea surface area thereof and also the hole-and-electron recombinationregion in which the luminous molecules 103 are present is made porous toenlarge a surface area thereof, can produce the emission with increasedluminance. In addition, the leveled layer 102 comprising the chargetransport material is provided on the surface of the organic layer 104as was made porous, thus producing the results that joint surfaces ofadjoining electrodes (cathodes 101) can be kept smooth; that leakage ofcurrent can be prevented; and that the hole or the electron can beinjected and transported with efficiency.

Also, the filling of the charge transport material into the porousorganic layer 104 enables the hole or the electron to be injected ortransported with efficiency.

The coloring matters whose quantum efficiency is nearly 1, includinglaser dyes such as coumarin 6, DCM and phenoxazone 9, are preferablyused for the luminous molecules 103. In addition to this, fused rings,such as naphthalene, anthracene, pyrene, and naphthacene, andderivatives thereof are also preferable. For example, rubrene hasquantum efficiency of nearly 1 and is also an efficient luminousmaterial. In addition, metal complexes, such as Alq and derivativethereof and beryllium benzoquinoline, are also preferable.

The charge transport material that is filled in the porous organic layer104 or forms the leveled layer 102 must transport the charge reverse inpolarity to the charge transported by the porous organic layer 104.

When the porous organic layer 104 is formed as the hole transportorganic layer, the electron transport material is chosen as the chargetransport material. On the other hand, when it is formed as the electrontransport organic layer, the hole transport material is chosen as thecharge transport material.

The electron transport materials that may preferably be used include lowmolecular weight material easy to enter the interior of the porouslayer. Metal complex, such as Alq and tris (4-methyl-8-quinolinolato)aluminum, electron deficient compound, such as 4,4,8,8-tetrakis(1H-pyrazole-1-yl) pyrazabole, and3-(2′-benzothiazolyl)-7-diethylaminocoumarin can be cited as thepreferable material. Materials having the hole blocking function, suchas bathocuproine and triazole derivative, are also preferable.

The hole transport materials that may be preferably be used includederivative having triphenylamine as fundamental skeleton. For example,tetraphenylbenzidine compound, triphenylamine trimer and benzidine dimerdisclosed by Japanese Laid-open (unexamined) Patent Publication No. Hei7-126615, various triphenyldiamine derivatives disclosed by JapaneseLaid-open (unexamined) Patent Publication No. Hei 8-48656, and MTPD(common name: TPD) disclosed by Japanese Laid-open (unexamined) PatentPublication No. Hei 7-65958 are preferable.

The hole transport material, when filled in the porous layer, can bereplaced by the electron injection material.

The electron injection materials that may preferably be used includedilithium phthalocyanine, disodium phthalocyanine, magnesium porphin,4,4,8,8-tetrakis (1H-pyrazole-1-yl) pyrazabole disclosed by JapanesePatent Application No. Hei 11-214712. The hole injection material thatmay preferably used include copper phthalocyanine,5,10,15,20-tetraphenyl-21H,23H-porphin copper (In Embodiment 2-2mentioned later, even when the roughened surface is smoothened to theorder of 10 nm, the electron injection material may be replaced by thecharge injection material).

In addition to the low molecular weight material, polymeric material maybe chosen as the material to be filled in the porous layer, but sincethere is the possibility that the material could not be fully filledtherein by only the application, some measurement, such asheat-treatment at glass transition point, should be taken to thoroughlypenetrate the material into the porous layer (In Embodiment 2-2mentioned later, the polymeric material may be chosen even for fillingthe roughened surface).

In consideration of making the organic layer porous, organic polymer ispreferable for the material to form the organic layer 104. Particularly,when it is made to be porous, the polymer-based organic compound ischosen, since it is subjected to the wet etching process (In Embodiment2-2 mentioned later, the organic polymer is preferable even for fillingthe roughened surface).

Material for general purpose applications, such aspoly-p-phenylenevinylene (PPV), polyvinyl carbazol (PVK),polymethylmethacrylate (PMMA), polyfluorene and derivatives thereof canbe used as the organic polymers to form the organic layer. Further, forthe purpose of improving the charge transport capabilities, the electrontransport material and the hole transport material may be mixed. Thematerial for general purpose applications may be used.

Preferably, the organic layer is formed to have thickness of 10-1,000nm. Preferably, the thickness of the region to be made porous of theorganic layer falls within about one-third of the whole thickness of theorganic layer, or particularly preferably in the range of 5-50 nm. Whenthe organic layer is reduced in thickness to 10 nm or less,short-circuit is caused when a voltage is applied. On the other hand,when it is increased 1,000 nm or more, the applied voltage is increasedand the luminous efficiency is reduced. Also, when the region to be madeporous is more than one-third of the whole organic layer or more than 50nm, the organic layer is reduced in density, so that the chargetransport performance is deteriorated and also stiffness and adhesion ofthe layer to the substrate is weakened. On the other hand, when theregion to be made porous is less than 5 nm, the above-mentioned effectsare not easily produced (In the embodiment 2-2 mentioned later, the sameapplies to the region to be roughened). In the applied organic layer, itis necessary that the uniform layer should be formed by deposition,first, from the viewpoint of the injection and transport of charge. Whenviewed microscopically, the organic polymer layer is rough, but the termof “uniform layer” used herein means that the layer is uniform whenviewed macroscopically. It is necessary that the roughness of thesurface of the deposited layer should be set within 5 nm at least.Making the organic polymer layer porous and rough means that theroughness of the uniformly deposited layer is further increased.

Referring now to FIG. 16, the producing method of the organiclight-emitting device will be described. FIG. 16 shows schematicsectional views illustrating the producing method of the organiclight-emitting device according to the embodiment 2-1 of the presentinvention.

(1) First, an anode 105 is formed on a substrate 106, as shown in FIG.16(a) (Anode forming step).

(2) Then, a medium 104′ is disposed over the substrate 106, as shown inFIG. 16(b). The medium 104′ means the coating film that is produced bythe application of the solution obtained by two kinds of material, i.e.,organic polymer and organic material that can be eluted to make thelayer porous being dissolved in solvent (Medium disposing step).

(3) Then, the medium 104′ is dried by heating or by airstream andtreated by use of the solvent that does not allow solubilization of theorganic polymer and allows solubilization of only the organic material,so as to elute only the organic material, as shown in FIG. 16(c). Then,the region where the organic material are present is hollowed andthereby the organic polymer layer is made porous to thereby produce theorganic layer 104 (Porosity producing step).

In the porosity producing step, at least a part of the organic layer104, to be more specific, at least one of a part of the organic layer104 on the anode 105 side and a part of the same on the cathode 101 sidecan be made porous.

(4) Then, luminous molecules 103 are dispersed over the organic layer104, as shown in FIG. 16(d) (Luminous molecule dispersing step).

(5) Then, a leveled layer 102 comprising the charge transport materialis formed on the organic layer 104, as shown in FIG. 16(e) (Leveledlayer forming step).

(6) Then, the cathode 101 is formed on the leveled layer 102, as shownin FIG. 16(f) (Cathode forming step).

The proportion of the organic material to be mixed with the organicpolymer is preferable 10-50%. This is because when the proportion of theorganic material is less than 10%, the layer (organic layer) cannotfully be made porous, while on the other hand, when the proportion ofthe organic material is more than 50%, the concentration of the layer islowered, so that the charge transport capabilities of the entire layeris deteriorated and the stiffness and adhesion of the layer to thesubstrate is weakened. The proportion of the organic material is furtherpreferably 20-30%.

The organic materials that may be chosen for use include oligomerproduced with low molecular weight for wide selection of the solvent, inaddition to the organic polymer.

The dispersion of the luminous molecules is preferably performed in theevaporation method. The luminous molecules may be brought into solutionso that they can be steamed. In the method for penetrating the luminousmolecules into the porous organic layer, the luminous molecules arepreferably steamed after dispersed (In the embodiment 2-2 mentionedlater as well, the luminous molecules are preferably steamed afterdispersed).

The organic light-emitting device is enabled to take out the surfaceemission by making at least one electrode transparent or translucent.Usually, the ITO (indium tin oxide) film is often used for the anodeserving as the hole injection electrode. Tin oxide, Ni, Au, Pt and Pdcan additionally be cited as the material therefor. The ITO film isformed by use of the deposition method, such as sputtering, electronbeam evaporation and ion plating, for the purpose of improving thetransparency or reducing the resistivity.

The film thickness is determined from the required sheet resistance andvisible light transmittance. The organic light-emitting device isrelatively high in driving current density, so that it is often usedwith thickness of 100 nm or more in order to reduce the sheetresistance.

An alloy comprising a metal of low work function and low electroninjection barrier, such as MgAg alloy or AlLi alloy proposed by Tang etal., and a metal of relatively large work function and stable is oftenused for the cathode serving as the electron injection electrode. Forthe purpose of the metal of low work function being deposited on theorganic layer side to protect the metal of low work function, the metalof large work function may be laminated thickly. Alternatively, alaminated electrode, such as Li/Al and LiF/Al, may be used therefor.These cathodes are preferably formed in the evaporation method or thesputtering method. When the electron injection material, such asdilithium phthalocyanine, disodium phthalocyanine, magnesium porphin,4,4,8,8-tetrakis (1H-pyrazole-1-yl) pyrazabole, is used for theelectrode, the electrode can be formed by only the metal of large workfunction and stable. This makes it resistant to reaction such asoxidizing and thus enables an enhanced life property.

The substrate may be formed of any material that can support the organiclight-emitting device laminating the thin film thereon and istransparent or translucent to take out the emission generated in theorganic layer. Glass such as Corning 1737 or polyester or other resinfilm may be used therefore.

FIG. 17 is a schematic sectional view showing a variant of the organiclight-emitting device according to the embodiment 2-1 of the presentinvention.

As shown in FIG. 17, the organic light-emitting device 107 has theconstitution in which the luminous molecules 103 of the materialcontributable to the emission are penetrated in the porous organic layer104 in the vicinity of the front surface. The luminous molecules 103 canbe penetrated in the porous organic layer 104 in the vicinity of thefront surface by steaming.

This constitution enables the luminous molecules 103 to be collected inthe porous organic layer 104 in the vicinity of the front surfacethereof and also enables the surface area in the hole-and-electronrecombination region in which the material contributable to the emissionto be enlarged, thus enabling the emission with high luminance. Theluminous molecules may be disposed on and in the vicinity of the frontsurface of the organic layer 104.

EXPERIMENTAL EXAMPLE 2-1

Experimental Example 2-1 illustrates an actual example of the organiclight-emitting device of the embodiment 2-1. In the following, thedescription thereon will be given.

Polyvinyl carbazol and butyral resin of low degree of polymerization(available from Sekisui Chemical Co., Ltd., S-LEC B, Part number BL-S)were dissolved in toluene in the proportion 80:20 by weight, to producethe solution.

Then, the solution thus produced was deposited on the ITO-depositedglass substrate in the spin coat method to produce the organic layerhaving thickness of 100 nm.

The ITO substrate forming thereon the organic layer was dipped inN,N-diimethylformamide, so that only the butyral resin (S-LEC B) wasdissolved and removed and, thereafter, it was dried at 200° C. byheating, to thereby produce the porous organic layer.

After the substrate was cooled down to room temperature in a vacuumchamber, the coumarin 6 of laser dyes used as the luminous moleculeswere dispersed on it at an evaporation rate of 0.01 nm/s for 10 secondsby resistance heating.

Sequentially, 4,4,8,8-tetrakis (1H-pyrazole-1-yl) pyrazabole used as theelectron injection material was evaporated at the evaporation rate of0.01 nm/s for 1 minute.

Finally, an Al electrode was formed at the evaporation rate of 1 nm/s tohave layer thickness of about 100 nm and thereby the organiclight-emitting device.

When the section of the device was observed by SEM, it was found thatthe porous layer having diameter of the order of 3-6 nm was formed andthe porous region was filled with the electron injection material. Whena direct current voltage was applied to this device for evaluationpurpose, it was found that the green luminescence of coumarin 6 wasobtained and glowed on stably with current efficiency of 8.0 cd/A.

TABLE 2 Current efficiency (cd/A) Experimental Example 2-1 8.0Experimental Example 2-2 8.2 Experimental Example 2-3 7.5 ExperimentalExample 2-4 3.2

EXPERIMENTAL EXAMPLE 2-2

In the organic light-emitting device of the experimental example 2-2,4,4,8,8-tetrakis (1H-pyrazole-1-yl) pyrazabole was evaporated at theevaporation rate of 0.1 nm/s for 2 minutes to thereby produce a leveledlayer, for the purpose of providing the leveled layer, instead offilling the porous layer with the electron injection material, in theevaporation of the electron injection material of the experimentalexample 2-1.

When the section of the device was observed by SEM, it was found thatthe leveled layer was formed on the porous layer having diameter of theorder of 3-6 nm. When a direct current voltage was applied to thisdevice for evaluation purpose, it was found that the green luminescenceof coumarin 6 was obtained and glowed on stably with current efficiencyof 8.2 cd/A.

EXPERIMENTAL EXAMPLE 2-4

The experimental example 2-4 is for comparison with the experimentalexamples 2-1 and 2-2 (the organic layer is not made porous).

Polyvinyl carbazol, 2-(4-biphenyl)-5-(4-tertbuthylphenyl)-1,3,4-oxadiazole used as the electron transport material,and coumarin 6 used as the luminous molecule material were dissolved ina weight ratio of 100:40:0.2 in the mixed solvent with a ratio oftoluene to THF of 1:1 to produce the silution.

Thereafter, the solution was applied to the ITO deposited glasssubstrate by use of the spinner, to form the organic layer havingthickness of 100 nm.

The cathode comprising Li and Al of 1 nm used as the electron injectionelectrode was formed on that organic layer, to thereby produce theorganic light-emitting device.

When a direct current voltage was applied to this device for evaluationpurpose, it was found that the green luminescence of coumarin 6 wasobtained and the current efficiency was 3.2 cd/A, as shown in TABLE 2.

Thus, the organic light-emitting device having the organic layer as wasmade porous was dramatically improved in current efficiency, as comparedwith the one having the organic layer as was not made porous.

Embodiment 2-2

Embodiment 2-2 relates to the organic light-emitting device having thestructure in which the emission region is roughened. FIG. 18 is aschematic sectional view of an organic light-emitting device accordingto the embodiment 2-2 of the present invention.

As shown in FIG. 18, an organic light-emitting device 110 comprises theanode 105, the cathode 101 arranged in opposition to the anode 105, anemission region 113 arranged between the anode 105 and the cathode 101,and a leveled layer arranged between the cathode 101 and the emissionregion 113.

The emission region 113 comprises an organic layer 120 which is madeporous on the cathode 101 side thereof and the luminance molecules 103arranged on the roughened front surface of the organic layer 120.

Further, the leveled layer 102 comprising charge transport material isformed on the organic layer 120 and the cathode 101 is laminated on theleveled layer 102.

This constitution, in which the luminous molecules 103 are collected onthe emission region 113 (on the front surface of the organic layer 120)which is roughened to enlarge its surface area and also thehole-and-electron recombination region in which the luminous molecules103 are present is roughened to enlarge its surface area, can producethe emission with increased luminance. It is to be noted that as is thecase with the embodiment 2-1, the luminous molecules may be penetratedin the organic layer in the vicinity of the front surface thereof or mayalternatively be arranged on as well as in the vicinity of the frontsurface of the organic layer.

Referring now to FIG. 19, the producing method of the organiclight-emitting device will be described. FIG. 19 shows schematicsectional views illustrating the producing method of the organiclight-emitting device according to the embodiment 2-2 of the presentinvention.

(1) The anode 105 is formed on the substrate 106 in the same manner asin the step (1) of the producing method as illustrated in Embodiment 2-1(FIG. 19(a)).

(2) Then, a coating film 120′ of a medium is formed on the anode 105 byuse of organic polymer forming the organic layer (FIG. 19(b)).

(3) Then, the coating film 120′ is etched by dry etching using e.g. areactive ion etching (RIE) to roughen the front surface of the coatingfilm 120′ so as to form the organic layer 120 (FIG. 19(c)).

(4) Then, the luminous molecules 103 are dispersed on the roughenedfront surface of the organic layer 120 (FIG. 19(d)). The dry etching maybe performed by use of a general purpose etching device such as a barreltype one and a parallel flat-plate type one. Depending on the state ofthe organic layer, Ar gas may simultaneously be introduced.

(5) Then, the leveled layer 102 comprising the charge transport materialis formed on the organic layer 120 in the same manner as in Embodiment2-1 (FIG. 19(e)).

(6) Then, the cathode 101 is formed on the leveled layer 102 (FIG.19(f).

EXPERIMENTAL EXAMPLE 2-3

Experimental Example 2-3 shows an actual example of the organiclight-emitting device of Embodiment 2-2. Specifically, the solution inwhich polyvinyl carbazol was dissolved in toluene was deposited on theITO-deposited glass substrate in the spin coat method to produce theorganic layer having thickness of 100 nm.

Then, the ITO substrate forming thereon the organic layer was roughenedin the dry etching device of parallel flat-plate type in the conditionsof: an oxygen flow rate of 60 sccm; pressure of 40 mTorr; andhigh-frequency output power of 100W for 1 minute and then was disposedin the vacuum chamber.

Then, the coumarin 6 of laser dyes used as the luminous molecules weredispersed on the substrate at an evaporation rate of 0.01 nm/s for 10seconds in the vacuum evaporation method using the resistance heating.

Sequentially, 4,4,8,8-tetrakis (1H-pyrazole-1-yl) pyrazabole used as theelectron injection material was evaporated at the evaporation rate of0.1 nm/s for 2 minutes.

Finally, the Al electrode was formed at the evaporation rate of 1 nm/sto have layer thickness of about 100 nm and thereby the organiclight-emitting device.

When the section of the device was observed by SEM, it was found thatthe roughened surface of the order of ±3 nm and the leveled layer formedby the electron injection material were formed in the organic layer.When a direct current voltage was applied to this device for evaluationpurpose, it was found that the green luminescence of coumarin 6 wasobtained and glowed on stably with current efficiency of 7.5 cd/A, asshown in TABLE 2.

Thus, the organic light-emitting device shown in Experimental example2-3 was dramatically improved in current efficiency by roughening theorganic layer, as compared with the organic light-emitting device shownin Experimental example 2-4.

Embodiment 2-3

While Embodiments 2-1 and 2-2 relate to the organic light-emittingdevices having the structure in which the emission region is made porousor roughened to produce improved luminous efficiency, this embodiment2-3 relates to the organic light-emitting device having the structure inwhich the charge transport region is roughened. FIG. 20 is a schematicsectional view showing an organic light-emitting device according to anembodiment 2-3 of the present invention.

As shown in FIG. 20, an organic light-emitting device 115 comprises theanode 105, the cathode 101 arranged in opposition to the anode 105, anemission region 117 arranged between the anode 105 and the cathode 101,and a charge transport layer 116 arranged between the emission region117 and the anode 105.

The charge transport layer 116 is roughened at the emission region 117side by the dry etching. In the structure above, the charge transportlayer 116 is the hole transport layer.

This constitution can provide an enhanced contact area of the emissionregion 117 and the charge transport region 116 and an improved injectionefficiency of the holes injected from the anode 105 to the emissionregion 117.

While in this embodiment, reference is given to the constitution of thecharge transport region being roughened, it is needless to say that thecharge transport region may be made porous to achieve the equivalenteffect to the effect produced by roughening the charge transport region.When the charge transport layer 116 has luminescent properties, theemission region 117 is not necessarily needed, but instead at leasteither of the anode 105 side and the cathode 101 side of the chargetransport layer 116 may be made porous or roughened to produce animproved injection efficiency of the charge from the electrode, as isthe case with the above.

INDUSTRIAL APPLICABILITY

As mentioned above, the constitution of the present invention can attainthe objects of the present invention satisfactorily.

According to the invention of the first inventive group, the luminousmolecules, or the luminous molecules and the charge transport materialare penetrated in the polymer, or the polymer in which the chargetransport material is dispersed, to thereby provide the organiclight-emitting device capable of producing an improved luminousefficiency and at the same time facilitating the patterning even in thepolymer dispersed organic light-emitting device.

According to the invention of the second inventive group, in thepolymer-based organic light-emitting device, the emission region, whichwas commonly diffused over the whole organic layer, is collected to aspecific region and also the hole-and-electron recombination regionwhere the luminous molecules are present is made porous or roughened toenlarge the surface area, to thereby produce an improved luminousefficiency.

1. A light-emitting device, comprising: an anode and a cathode having anemission region therebetween, wherein the emission region comprisesmaterial contributable to emission and a medium for containing thematerial, wherein the material contributable to the emission has asubstantially successive distribution of concentration from the anodeside of the emission region toward the cathode side thereof, and whereina part of the emission region that exhibits a maximum concentration ofthe material contributable to the emission is away from the anode andthe cathode.
 2. The light-emitting device as set forth in claim 1,wherein the emission region further comprises charge transport material.3. The light-emitting device as set forth in claim 2, wherein the chargetransport material has a substantially successive distribution ofconcentration from the anode side of the emission region toward thecathode side thereof.
 4. The light-emitting device as set forth in claim1, wherein the emission region comprises, at the side of the emissionregion near the anode or the cathode, a region where the materialcontributable to the emission is not present.
 5. A lighting devicecomprising in combination therewith the light-emitting device as setforth in claim
 1. 6. A light-emitting device, comprising: an anode and acathode having a charge transport region therebetween, wherein thecharge transport region comprises charge transport material and a mediumfor containing the charge transport material wherein the chargetransport material has a substantially successive distribution ofconcentration from the cathode side of the charge transport regiontoward the anode side thereof, and wherein a part of the chargetransport region that exhibits a maximum concentration of the chargetransport material is away from the anode and the cathode.
 7. Thelight-emitting device as set forth in claim 6, wherein the chargetransport region comprises, at the side of the emission region near theanode or the cathode, a region where the charge transport material isnot present.
 8. A light-emitting device, comprising: an anode and acathode having an emission region therebetween, wherein the emissionregion comprises material contributable to emission and a medium forcontaining the material, and wherein the material contributable to theemission has a distribution of concentration that reduces substantiallysuccessively in a direction parallel to a surface of the cathode and asurface of the anode from a substantially center of the emission regiontoward a periphery thereof.
 9. The light-emitting device as set forth inclaim 8, wherein said material contributable to emission is a pluralityof materials contributable to emission adjacently arranged in adirection parallel to a surface of the cathode and a surface of theanode, wherein each of the plurality of materials contributable toemission is different in luminous color from others of said plurality ofmaterials.
 10. The light-emitting device as set forth in claim 8,wherein the emission region further comprises charge transport material.11. The light-emitting device as set forth in claim 10, wherein thecharge transport material has a distribution of concentration thatreduces in the direction parallel to the surface of the cathode and thesurface of the anode from the substantially center of the emissionregion toward the periphery thereof.
 12. The light-emitting device asset forth in claim 11, wherein the charge transport material has asubstantially successive distribution of concentration from the cathodeside of the emission region toward the anode side thereof.
 13. Thelight-emitting device as set forth in claim 8, wherein the materialcontributable to the emission has a substantially successivedistribution of concentration from the cathode side of the emissionregion toward the anode side thereof.
 14. The light-emitting device asset forth in claim 8, wherein the emission region includes a regionwhere the material contributable to the emission is not present.
 15. Thelight-emitting device as set forth in claim 8, wherein the medium forcontaining the material contributable to the emission has chargetransport capabilities.
 16. The light-emitting device as set forth inclaim 8, wherein the medium for containing the material contributable tothe emission comprises organic material.
 17. The light-emitting deviceas set forth in claim 8, wherein the medium comprises a polymer.
 18. Adisplay comprising in combination therewith the light-emitting device asset forth in claim
 8. 19. A method of producing a light-emitting devicehaving an emission region between an anode and a cathode, the methodcomprising: locating a medium on the anode or the cathode; andcontaining material contributable to emission and charge transportmaterial in the medium; wherein said containing comprises penetratingthe material contributable to the emission and the charge transportmaterial into the medium, so that said materials are contained in themedium.
 20. A method of producing a light-emitting device having anemission region between an anode and a cathode, the method comprising:locating a medium on the anode or the cathode; and containing materialcontributable to emission and charge transport material in the medium;wherein said containing comprises bringing a solution comprising thematerial contributable to the emission and the charge transport materialdissolved in solvent into contact with the medium, so that the materialsare penetrated into the medium.
 21. A light-emitting device, comprising:an anode and a cathode having an emission region therebetween, whereinthe emission region comprises material contributable to emission and amedium comprising organic material for containing the material, whereinat least one of an anode side of the emission region and a cathode sidethereof is porous, and wherein the material contributable to emission iscollected and included in a surface of the emission region which isporous.
 22. The light-emitting device as set forth in claim 21, whereincharge transport material is included in a surface of the emissionregion which is porous.
 23. The light-emitting device as set forth inclaim 21, wherein a leveled layer comprising charge transport materialis located on a surface of the emission region which is porous.
 24. Thelight-emitting device as set forth in claim 21, wherein the emissionregion comprises a polymer.
 25. A display comprising in combinationtherewith the light-emitting device as set forth in claim
 20. 26. Alighting device comprising in combination therewith the light-emittingdevice as set forth in claim
 21. 27. A light-emitting device,comprising: an anode and a cathode having an emission regiontherebetween, wherein the emission region comprises materialcontributable to emission and a medium comprising organic material forcontaining the material, wherein at least one of an anode side of theemission region and a cathode side thereof is porous, and wherein thematerial contributable to emission is collected and included in a regionin the vicinity of a surface of the emission region which is porous. 28.A light-emitting device, comprising: an anode and a cathode having acharge transport region therebetween, wherein the charge transportregion comprises material contributable to emission and a mediumcomprising organic material for containing the material, and wherein atleast one of an anode side of the charge transport region and a cathodeside thereof is porous.
 29. The light-emitting device as set forth inclaim 28, wherein the charge transport region is a hole transportregion.
 30. The light-emitting device as set forth in claim 28, whereinthe charge transport region is an electron transport region.
 31. Alight-emitting device, comprising: an anode and a cathode having anemission region therebetween, wherein the emission region comprisesmaterial contributable to emission and a medium comprising organicmaterial for containing the material, wherein at least one of an anodeside of the emission region and a cathode side thereof is a roughenedside, and wherein the material contributable to emission is collectedand included in a surface of the roughened emission region.
 32. Thelight-emitting device as set forth in claim 31, wherein a leveled layercomprising charge transport material is provided on a roughened surfaceof the emission region.
 33. The light-emitting device as set forth inclaim 31, wherein the emission region comprises a polymer.
 34. Alight-emitting device, comprising: an anode and a cathode having anemission region therebetween, wherein the emission region comprisesmaterial contributable to emission and a medium comprising organicmaterial for containing the material, wherein at least one of an anodeside of the emission region and a cathode side thereof is a roughenedside, and wherein the material contributable to emission is collectedand included in a region in the vicinity of a roughened surface of theemission region.
 35. A light-emitting device, comprising: an anode and acathode having a charge transport region therebetween, wherein thecharge transport region comprises material contributable to emission anda medium comprising organic material for containing the material, andwherein at least one of an anode side of the charge transport region anda cathode side thereof is a roughened side.
 36. The light-emittingdevice as set forth in claim 35, wherein the charge transport region isa hole transport region.
 37. The light-emitting device as set forth inclaim 35, wherein the charge transport region is an electron transportregion.
 38. A method of producing a light-emitting device having anemission region between an anode and a cathode, the method comprising:locating a medium comprising organic material on the anode or thecathode; and making at least a part of the medium comprising organicmaterial porous.
 39. A method of producing a light-emitting devicehaving an emission region between an anode and a cathode, the methodcomprising: locating a medium comprising organic material on the anodeor the cathode; making at least one of an anode side of the mediumcomprising organic material and a cathode side thereof porous; andlocating material contributable to emission on a porous surface of themedium comprising organic material, so that the emission region isformed by the medium and the material contributable to the emission. 40.The method of producing a light-emitting device as set forth in claim39, further comprising locating charge transport material on a poroussurface of the emission region.
 41. The method of producing alight-emitting device as set forth in claim 39, further comprisingforming a leveled layer comprising charge transport material on theemission region.
 42. The method of producing a light-emitting device asset forth in claim 39, comprising locating a medium containing materialsoluble in a specified solvent, and eluting the soluble material fromthe solvent to thereby make the medium porous.
 43. A method of producinga light-emitting device having an emission region between an anode and acathode, the method comprising: locating a medium comprising organicmaterial on the anode or the cathode; making at least one of an anodeside of the medium comprising organic material and a cathode sidethereof porous; containing material contributable to emission in aregion in the vicinity of a porous surface of the medium comprisingorganic material, so that the emission region is formed by the mediumand the material contributable to the emission; and locating chargetransport material on a porous surface of the medium.
 44. A method ofproducing a light-emitting device having an emission region between ananode and a cathode, the method comprising: locating a medium comprisingorganic material on the anode or the cathode; and roughening a part ofthe medium comprising organic material.
 45. A method of producing alight-emitting device having an emission region between an anode and acathode, the method comprising: locating a medium comprising organicmaterial on the anode or the cathode; roughening at least one of ananode side of the medium comprising organic material and a cathode sidethereof; and locating material contributable to emission on a roughenedsurface of the medium comprising organic material, so that the emissionregion is formed by the medium and the material contributable to theemission.
 46. The method of producing a light-emitting device as setforth in claim 45, further comprising forming a leveled layer comprisingcharge transport material on the emission region.
 47. The method ofproducing a light-emitting device as set forth in claim 45, comprisingroughening the emission region by dry etching.
 48. A method of producinga light-emitting device having an emission region between an anode and acathode, the method comprising: locating a medium comprising organicmaterial on the anode or the cathode; roughening at least one of ananode side of the medium comprising organic material and a cathode sidethereof; and containing material contributable to emission in a regionin the vicinity of a roughened surface of the medium comprising organicmaterial, so that the emission region is formed by the medium and thematerial contributable to the emission.